By Linda Weber

Selecting the right prosthetic liner for an amputee patient is a complex problem that clinicians grapple with daily. They find themselves constantly weighing trade-offs between liner features.

Cushioning and comfort inevitably must be balanced with durability. More cushioning decreases how long the liner will maintain its shape and protective properties before deteriorating. But a thicker liner adds weight and decreases the ability to control the limb. A thinner liner may provide better functionality, but reduce comfort.

But the criteria for choosing a prosthetic liner go beyond comfort and functionality. Practitioners also consider whether the liner will maintain a close fit, preserve secure suction suspension, minimize movement within the socket, reduce perspiration buildup, and prevent skin irritation and breakdown.

And then there are individual patient attributes to factor in. Among these are the amputation level; the type of suspension system used; and the shape and condition of the limb, including the amount of tissue padding, socket design, activity level, and skin sensitivity.

Surprisingly, few studies have been attempted that pinpoint which liners work best. A June 2010 literature review in Prosthetics and Orthotics International looked at 14 scientific articles that met eligibility criteria. The results showed that although liner material properties have been well studied, their effect on function is not well understood.

Because little scientific evidence is available upon which to base their decisions, prosthetists rely heavily on their own experience and what they glean from colleagues. This means that each practitioner’s process is different.

Suspension type directly affects the choice of liner material and the way the liner is designed, said Jack Uellendahl, CPO, who works for Hanger Prosthetics and Orthotics in both Phoenix and Denver.

“Pin suspension liners should not allow distal elongation,” he said. “Elevated vacuum suspension should be used with a liner that does not thin out but has good ability to flow and then return to the undistorted shape quickly and repeatedly.”

According to Uellendahl, the transfemoral liner doesn’t need to be as thick as that required for a transtibial amputee, because the transfemoral limb is more generously padded with muscle and soft tissue. Transtibial amputees also require a liner that allows range of motion at the knee. This can be done by preflexing the liner, or through other means such as corrugation, thinning, or using more elastic material around the knee.

Pin suspension may be another alternative for increasing knee flexion, according to Scott Sabolich, CP, LP, owner and clinical director of Scott Sabolich Prosthetics and Research in Oklahoma City.

“If severe knee flexion is needed then we look at a pin-type liner,” he said. “Overall, though, we are not big pin fans.”

Sabolich and Uellendahl both primarily use off-the-shelf liners to keep costs down. Sabolich maintains that a 6-mm liner will fit 90% of the population.

“We find the best scenario is with a cushion 6-mm liner and a passive one-way valve with a thin soft silicone suspension sleeve,” he said. “You only need 9 mm on major scar tissue [patients] and usually 3 mm on people that really don’t need liners like KDs (knee disarticulations) or long BKs.”

Sabolich cautions fellow practitioners about buying into the hype of new products.

“The problem is that every new cool product is not always that cool and isn’t necessarily good for everyone,” he said.

This doesn’t mean Sabolich is against innovation. He encourages others to try new things—whether it’s liners, feet, or knees—but not to give up on what works. He’s also a firm believer in being upfront with patients when trying something new.

“Don’t experiment on someone while giving [him or her] the idea that you do these things all the time,” he advised. “If you have never fit a seal-in liner, but want to try one, ask the patient first if it’s okay. Allow them to have a say in their choice of liners, components, and setup, but guide them in those choices.”